There are various industrial or commercial applications where a multi-port valve assembly must be used to direct an incoming fluid into one or more of a plurality of outlet ports. For instance, conventional vapor cycle refrigerant systems employ a vapor compressor to compress the refrigerant vapor, a condenser where the vapor is cooled and liquified, an expansion valve where liquid pressure is reduced, and an evaporator where the refrigerant is vaporized. Refrigerant enters the expansion valve as a liquid and leaves as a low pressure mixture of liquid and vapor. Where multiple evaporators are used in parallel, the refrigerant quality may not be the same in each of the parallel paths. In other words, one evaporator may receive mostly liquid and another may receive mostly vapor. This results in the cooling capacity of the evaporators being unequal.
With such systems as described above, there is a need to provide equal cooling capacity in the plurality of parallel evaporators by insuring that each evaporator receives the same mass flow of fluid at the same quality. One problem in designing valves for such applications is that the flow areas of the plurality of outlet ports are quite small and therefore difficult to manufacture uniformly. In other words, the primary cause of non-uniform flow through the multiple ports concerns variances in manufacturing tolerances. There may be different downstream resistances or different downstream pressure drops. For instance, there may be differences in the length of tubes connected to the valve ports.
Therefore, the invention is directed to providing a multi-port valve assembly, such as a multi-port refrigerant proportioning valve, which has a common inlet and a separate metering valve element or member for each of a plurality of output ports or lines leading to a corresponding plurality of evaporators, for instance, with all of the valve elements being movable conjointly or simultaneously. Since metering occurs in the liquid state and all metering valve elements are calibrated to have the same effective area, each evaporator receives an equal share of the total flow and cooling capacity is balanced among the evaporators.